Process for the continuous quaternisation of tertiary amines with an alkyl halide

ABSTRACT

The present invention relates to a continuous process for the quaternisation of tertiary amines with an alkyl halide. The process is performed at a temperature between 50° C. and 140° C. by reacting a tertiary amine and an alkyl halide in a tubular reactor at a pressure sufficient to keep the alkyl halide dissolved in the reaction mixture. The molar ratio between the tertiary amine and the alkyl halide is from 1:1.3 to 1:2.9 and the pressure is suitably between 12 to 65 bar. The process could be performed either with or without a solvent present, preferably without a solvent. The process gives high product yields and low amounts of by-products.

The present invention relates to a continuous process for thequaternisation of tertiary amines with an alkyl halide that is dissolvedin the reaction mixture.

Several methods for quaternisation of amines with alkyl halides havebeen disclosed. The quaternisation processes are performed within avariety of pressure and temperature ranges, and at different molarratios between the amine and the quaternising agent. There are includedembodiments both of batch-wise as well as continuous processes.

In EP 0 869 114 a quaternisation process is described where analkoxylated ester-amine is reacted with a quaternising agent at apressure of 1-50 bars. The process is batch-wise, and in the workingexamples the process is performed in a low-pressure autoclave with 1.025mole methyl chloride per mole ester-amine during 24 hours or more.

In U.S. Pat. No. 3,813,441 a continuous process for the manufacture ofquaternary ammonium chlorides is described, where a primary or asecondary amine is reacted with methyl chloride at a temperature of50-80° C. and at a pressure of 3 to 10 atm. The reaction is performed inthe presence of an aqueous solution of an alkali metal hydroxide and alower alcohol. Since a primary or secondary amine is the startingmaterial, sodium chloride is formed during the reaction and has to beremoved continuously.

U.S. Pat. No. 5,491,240 discloses in the working examples a batchprocess for the manufacture of a quaternary ammonium compound byreacting a tertiary amine stepwise with a quaternising agent, e.g.methyl chloride, at a pressure of maximum 62 psig (about 5.3 bar) duringreaction times of about 10 hours. Solvent is added intermittently if theviscosity gets too high, to maintain the reaction mixture in the liquidstate during the reaction.

EP 0 288 857 describes a quaternisation reaction between a tertiaryamine and an alkyl halide present in a molar ratio ranging from 1:3 to1:8 at a temperature between 50-150° C. at an over-pressure (18 and 27.5bar in the examples). The reaction is performed batch-wise in theabsence of solvents, and the quaternary ammonium compound is obtained inpowdered form. The reaction time stated in the examples was about 2hours. EP 0 012 296 and U.S. Pat. No. 4,275,235 describe a similarprocess using the same molar ratio range.

In U.S. Pat. No. 5,041,664 a continuous quaternisation process isdisclosed where a long chain tertiary amine and an alkyl chloride arereacted in the presence of a heterogeneous catalyst in the presence ofan alcohol solvent. The mole ratio between the amine and the chloride issuitably 1:1.2 to 1.2:1, preferably 1:1, and the pressure may be fromabout 1 to 210 bar. In the working example 70 bar is used.

The aim of the present invention is to create a continuous process forthe manufacture of quaternary ammonium compounds from tertiary aminesand alkyl halides, which is performed at moderate pressures andtemperatures, and with short reaction times and no need for solvents,nor for catalysts. The process should also give high product yields andlow amounts of by-products.

It has surprisingly been found that these objects can be fulfilled by acontinuous process for manufacturing a quaternary ammonium compound byreacting, at a temperature between 50° C. and 140° C., preferably from70° C. to 130° C. and most preferably from 80° C. to 125° C., a tertiaryamine and an alkyl halide in a tubular reactor at a pressure sufficientto keep the alkyl halide dissolved in the reaction mixture, preferablyat 12-65 bar, more preferably at 15-55 bar and most preferably at 18-50bar, the molar ratio between the tertiary amine and the alkyl halidebeing from 1:1.3 to 1:2.9, preferably from 1:1.4 to 1:2.7 and mostpreferably from 1:1.5 to 1:2.6. The process could be performed eitherwith or without a solvent present, preferably without a solvent.

There are several advantages connected with the process of the presentinvention.

Firstly, by using a pressure between 12 and 65 bar within the giventemperature interval, the alkyl halide will be present in a solutiontogether with the tertiary amine reactant, the quaternary ammoniumproduct formed during the reaction and optionally a solvent. Thereby theviscosity of the reaction mixture will be reduced. The reaction may evenbe performed without any solvent, which will lead to less by-productformation. To use a pressure above 65 bar will not give any additionaladvantages during the present conditions. No significant increase in thereaction rate will be achieved, and such a high pressure will requiremore expensive equipment. The optimal pressure depends for example onthe temperature and the type of alkyl halide chosen, but is normallyfrom 18 to 30 bar for a reaction performed in a solvent, and normallyfrom 30 to 50 bar for a solvent-free process. When a solvent, such as analcohol, is present during the quaternisation process, by-products, suchas ethers, may be formed from the solvent and the alkyl halide. Whenrecycling the unreacted alkyl halide, there will normally be a build-upof these by-products that may cause severe problems in the commercialproduction process, as well as for the quality of the desired quaternaryammonium products.

Secondly, by using a molar ratio of tertiary amine to alkyl halidebetween 1:1.3 and 1:2.9, there will be a smaller volume of the reactoroccupied by the alkyl halide and a smaller amount of alkyl halide torecycle as compared to the process described in the working examples inEP 0 288 857, where the ratio is 1:3.4.

Thirdly, a continuous process according to the invention, which resultsin a short residence time and makes optimal use of the available reactorspace, will give rise to a higher space time yield and a better qualityof the product, such as low colour.

Preferably the reaction mixture is blended with the aid of internals inthe tubular reactor. The presence of internals promotes plug-flowbehaviour of the reaction mixture, and will further increase thereaction rate and the production capacity of the tubular reactor.Suitable internals are for example an inert packing, such as glassraschig rings.

The temperature according to the invention varies within the range of 50to 140° C. At temperatures below 50° C. the reaction rate is notsufficient, and above 140° C. there is too much decomposition of thequaternary ammonium salt and formation of by-products. The temperaturerange is normally between 80 and 125° C.

The quaternary ammonium compounds that may be manufactured by theprocess of the present invention could have the formulaR₁R₂R₃R₄N⁺X⁻  (I)where R₁ is a hydrocarbyl group containing 1-22 carbon atoms, preferably1-4 carbon atoms; R₂ and R₃ are the same or different hydrocarbyl groupscontaining 1-22 carbon atoms, preferably 8-22 carbon atoms, which couldbe saturated or unsaturated, linear or branched, or a group (AO)_(y)Hwhere AO is an alkyleneoxy group with 2 or 3 carbon atoms, preferably 2carbon atoms, and y is a number between 1-50; R₄ is an alkyl groupcontaining 1-4 carbon atoms, preferably 1-2 carbon atoms; X⁻ is a halideanion, preferably Cl⁻, Br⁻ or I⁻ and most preferably Cl⁻. Thesequaternary compounds are obtainable by the process of the presentinvention by reacting a tertiary amine of the formula R₁R₂R₃N with analkyl halide of the formula R₄X, where X is halogen and R₁, R₂, R₃ andR₄ have the same meaning as in formula I. Suitable examples of thetertiary amines are di(tallow alkyl)methylamine, (tallowalkyl)dimethylamine, di(hydrogenated tallow alkyl)methylamine,(hydrogenated tallow alkyl)dimethylamine, di(rape seedalkyl)methylamine, (rape seed alkyl)dimethylamine, di(soyaalkyl)methylamine, (soya alkyl)dimethylamine, di(coco alkyl)methylamine,(coco alkyl)dimethylamine, distearylmethylamine, stearyl-dimethylamine,dilaurylmethylamine, lauryldimethylamine, polyethoxylated primaryamines, such as polyethoxylated cocoamine, polyethoxylated (tallowalkyl)amine and polyethoxylated (hydrogenated tallow alkyl)amine andpolyethoxylated secondary amines, such as polyethoxylated dicocoamine,polyethoxylated di(tallow alkyl)amine and polyethoxylateddi(hydrogenated tallow alkyl)amine.

Other quaternary ammonium compounds that may be formed by the process ofthe present invention have the formulaR₅R₆R₇N⁺(C_(p)H_(2p)) (OA)_(z)Q-R₈ X⁻  (II)where R₅ and R₆ independently is an alkyl group containing 1-6 carbonatoms, preferably 1-4 carbon atoms and most preferably 1-2 carbon atoms;R₇ is—-(CpH_(2p)) (OA)_(z)Q-R₈ or a hydrocarbyl group with 1-22 carbonatoms, preferably 1-6 carbon atoms, more preferably 1-4 carbon atoms andmost preferably 1-2 carbon atoms; R₈ is a hydrocarbyl group with 1-22carbon atoms, preferably 8-22 carbon atoms; Q is

p is a number from 1 to 6, preferably 2-3, OA is an oxyalkylene groupwith 2 or 3 carbon atoms, preferably 2 carbon atoms, z is a numberbetween 0 and 50; R₉ is H or a hydrocarbyl group with 1-22 carbon atomsand X⁻ has the same meaning as in formula I. R₈ and R₉ could besaturated or unsaturated, linear or branched. The products of formula IIinclude the so-called esterquats. These are obtainable by the process ofthe present invention by reacting a tertiary amine of formulaR₆R₇N(C_(p)H_(2p)) (OA)_(z)Q−R₈ with an alkyl halide of the formula R₅X,where Q is —C(═O)—O or —O—C(═O), X is halogen and R₅, R₆, R₇, R₈, p, OAand z have the same meaning as above. Suitable examples of thesetertiary amines are the diesters of stearic acid, coco fatty acid,tallow fatty acid, rape seed fatty acid, soya fatty acid, oleic acid,palmitic acid or lauric acid and methyldiethanolamine. Also included arethe amidoquats, which are obtained in an analogous manner from atertiary amine according to the above formula where Q is —N(R₉)—C(═O) or—C(═O)—N(R₉). Suitable examples of these tertiary amines are theamidoamines obtained from N,N-dimethylpropylenediamine and a fatty acidsuch as stearic acid, coco fatty acid, tallow fatty acid, rape seedfatty acid, soya fatty acid, oleic acid, palmitic acid or lauric acid.

Still another group of quaternary ammonium compounds that may beobtained by the process of the present invention has the formula

where each Y independently is H or —C(═O)—R₈, Σa+b+c is 3-50 and R₅, R₈and X⁻ have the same meaning as above. These quaternary ammoniumcompounds are esterquats that are obtainable by the process of thepresent invention from fatty acid esters of triethanolamine orethoxylated triethanolamine and an alkyl halide R₅X, where X is halogenand R₅ has the same meaning as in formula III. Suitable examples are theesters obtained from triethanolamine or ethoxylated triethanolamine andan acid selected from the group stearic acid, coco fatty acid, tallowfatty acid, rape seed fatty acid, soya fatty acid, oleic acid, palmiticacid and lauric acid.

The compounds that may be quaternised by the process of the presentinvention are not limited to the types mentioned above. For example,also tertiary amines selected from the group consisting of di- andpolyamines, alkoxylated di- and polyamines, 3-alkyloxypropylamines,alkoxylated 3-alkyloxypropylamines,N-(3-alkoxypropyl)-1,3-propanediamines, alkoxylatedN-(3-alkoxypropyl)-1,3-propanediamines, amidoamines and amino acids maybe quaternised. The only requirement is that the compound to bequaternised should contain a tertiary amino group and no primary orsecondary amino groups.

The alkyl halide used as the quaternising agent is preferably methylchloride, methyl bromide, ethyl chloride or ethyl bromide, and mostpreferably methyl chloride.

The following examples are illustrative of the invention, and should notbe construed as limiting thereof.

EXAMPLE 1

A 0.4 l tubular reactor with an internal diameter of 0.01 m, filled withan inert packing consisting of glass raschig rings, was used for thecontinuous reaction of 68 g/hour di(hydrogenated tallowalkyl)methylamine/isopropanol mixture with methyl chloride. The reactanttertiary amine/methyl chloride molar ratio was 1:1.6 (MW amine=523) andthe isopropanol content was 15% counted on tertiary amine. During thequaternisation the reactor temperature was kept at 100° C. and thereactor pressure was 20 bar. The resulting product was depressurized andcollected in a heated glass round bottom flask equipped with acondenser. The excess amount of methyl chloride was removed by nitrogenpurging. At a residence time of 3 hours the tertiary amine conversion tothe quaternary ammonium chloride was 97.5%. The desired product wasobtained in the form of a yellow clear liquid solution above 70° C.

EXAMPLE 2

The same equipment as described in example 1 was used for a continuousreaction of 102 g/hour diester of stearic acid andmethyldiethanolamine/ethanol mixture with methyl chloride at 100° C. and20 bar. The reactant tertiary amine/methyl chloride molar ratio was1:1.6 (MW amine=598) and the ethanol content was 15% counted on tertiaryamine. At a residence time of 2 hours the tertiary amine conversion tothe quaternary ammonium chloride was 97%. The desired product wasobtained in the form of a slightly yellow clear liquid solution above70° C.

EXAMPLE 3

The same equipment as described in example 1 was used for a continuousreaction of 68 g/hour diester of stearic acid and methyldiethanolaminewith methyl chloride at 100° C. and 35 bar. The reactant tertiaryamine/methyl chloride molar ratio was 1:2.5 (MW amine=598). At aresidence time of 3 hours the tertiary amine conversion to thequaternary ammonium chloride was 96%. After depressurization sufficientethanol was added to the product in order to obtain the desiredactivity, whereafter the remaining excess amount of methyl chloride wasremoved by nitrogen purging. The desired product was obtained in theform of a slightly yellow clear liquid solution above 70° C.

EXAMPLE 4

The same equipment as described in example 1 was used for a continuousreaction of 106 g/hour di(coco alkyl)methyl amine with methyl chlorideat 10° C. and 30 bar. The reactant tertiary amine/methyl chloride molarratio was 1:2.35 (MW amine=397). At a residence time of 2 hours thetertiary amine conversion to the quaternary ammonium chloride was 98%.After depressurization ethanol was added to the product in order toobtain a solution, whereafter the remaining excess amount of methylchloride was removed by nitrogen purging. The desired product wasobtained in the form of a slightly yellow clear liquid solution above70° C.

Comparison 1

The same equipment as described in example 1 was used for a continuousreaction of 68 g/hour diester of stearic acid andmethyldiethanolamine/isopropanol mixture with methyl chloride at 100° C.and 20 bar. The reactant tertiary amine/methyl chloride molar ratio was1:1.2 (MW amine=598) and the isopropanol content was 15% counted ontertiary amine. At a residence time of 3 hours the tertiary amineconversion to the quaternary ammonium chloride was 89%.

Comparison 2

The same equipment as described in example 1 was used for a continuousreaction of 68 g/hour diester of stearic acid andmethyldiethanolamine/isopropanol mixture with methyl chloride at 100° C.and 7 bar. The reactant tertiary amine/methyl chloride molar ratio was1:1.6 (MW amine=602) and the ethanol content was 15% counted on tertiaryamine. At a residence time of 3 hours the tertiary amine conversion tothe quaternary ammonium chloride was 88%.

Comparison 3

The same equipment as described in example 1 was used for a continuousreaction of 68 g/hour diester of stearic and methyldiethanolamine withmethyl chloride at 100° C. and 20 bar. The reactant tertiaryamine/methyl chloride molar ratio was 1:4 (MW amine=598). At a residencetime of three hours the tertiary amine conversion to the quaternaryammonium chloride was 89%. In Example 3 a conversion of 96% was achievedwith a molar ratio of only 1:2.5.

1. A continuous process for manufacturing a quaternary ammonium compoundby reacting, at a temperature of from 50° C. to 140° C., a tertiaryamine and an alkyl halide wherein the reaction is performed in a tubularreactor containing internals that are promoting plug-flow behaviour at apressure from 12 to 65 bar and sufficient to keep the alkyl halidedissolved in the reaction mixture, the molar ratio between the tertiaryamine and the alkyl halide being from 1:1.3 to 1:2.9.
 2. The process ofclaim 1 wherein the pressure is from 15 to 55 bar and the molar ratiobetween the tertiary amine and the alkyl halide is 1:1.4 to 1:2.7. 3.The process of claim 1 wherein the reaction mixture is, except for thealkyl halide, free from solvents.
 4. The process of claim 3 wherein thepressure is 30-50 bar.
 5. The process of claim 1 wherein the alkylhalide is selected from the group consisting of methyl chloride, methylbromide, ethyl chloride and mixtures thereof.
 6. The process of claim 1wherein the quaternary ammonium compound has the formulaR₁R₂R₃R₄N⁺X⁻  (I) where R₁ is a hydrocarbyl group containing 1-22 carbonatoms; R₂ and R₃ are the same or different hydrocarbyl groups containing1-22 carbon atoms or a group (AO)_(y)H, where AO is an alkyleneoxy groupwith 2 or 3 carbon atoms and y is a number between 1-50; R₄ is an alkylgroup containing 1-4 carbon atoms and X⁻ is a halide anion.
 7. Theprocess of claim 1 wherein the quaternary ammonium compound has theformulaR₅R₆R₇N⁺(C_(p)H_(2p)) (OA)_(z)Q-R₈ X⁻  (II) where R₅ and R₆independently is an alkyl group containing 1-6 carbon atoms; R₇ is—(CH₂) (OA)_(z)Q-R₈ or a hydrocarbyl group with 1-22 carbon atoms; R₈ isa hydrocarbyl group with 1-22 carbon atoms; Q is

p is a number from 1 to 6, OA is an oxyalkylene group with 2 or 3 carbonatoms, z is a number between 0 and 50; R₉ is H or a hydrocarbyl groupwith 1-22 carbon atoms, and X⁻ is a halide anion.
 8. The process ofclaim 1 wherein the quaternary ammonium compound has the formula

where each Y independently is H or —C(═O)—R₈, Σa+b+c is 3-50 and R₅ isan alkyl group containing 1-6 carbon atoms, R₈ is a hydrocarbyl groupwith 1-22 carbon atoms and X⁻ is a halide anion.
 9. (canceled) 10.(canceled)